Abstract:

The invention relates to a process for preparing (meth)acrylate-based ABA
triblock copolymers with a silyl functionalization of the A blocks.

Claims:

1. Block copolymers of composition ABA with at least 1 and at most 4
silyl groups per individual A block, characterized in that block A, a
copolymer containing silyl functionalized (meth)acrylates and monomers
selected from the group of (meth)acrylates or mixtures thereof, and one
block B, containing (meth)acrylates or mixtures thereof which have no
additional silyl function, are polymerized as ABA block copolymers.

2. Block copolymers according to claim 1, characterized in that the
individual A blocks of the ABA block copolymers have a composition with
at least 1 and at most 2 silyl groups.

3. Block copolymers according to claim 1 or 2, characterized in that the
individual A blocks each make up less than 25% of the total weight of the
ABA block copolymer.

4. Block copolymers according to claim 3, characterized in that the
individual A blocks each make up less than 10% of the total weight of the
ABA block copolymer.

5. Block copolymers according to claim 1 to 4, characterized in that the
individual B blocks may in turn inherently have a CDC triblock structure
and so lead to ACDCA pentablock copolymers.

6. Block copolymers according to claim 5, characterized in that the
composition of the C blocks corresponds to the composition of the
non-silyl-functionalized fraction in the A blocks.

7. Block copolymers according to claim 1, characterized in that the
individual A blocks may in turn inherently have a CA' diblock structure,
the blocks A' comprising monomers selected from the group of
(meth)acrylates or mixtures thereof, the C blocks containing no
silyl-functionalized (meth)acrylates, otherwise conforming to the
composition of the A' blocks and so leading to CA'BA'C pentablock
copolymers.

8. Block copolymers according to claim 1, characterized in that the
monomers used for functionalization of the A segments contain an
unsaturated, free-radically polymerizable group and a silyl group.

9. Block copolymers according to claim 8, characterized in that the
additional silyl group has the form
--Si(OR1)bR.sup.2.sub.aXc where the organic radicals
R1 and R2 are each identical or different to one another and
are selected from the group of aliphatic hydrocarbon radicals consisting
of 1 to 20 carbon atoms and being linear, branched or cyclic, and R1
may also exclusively be hydrogen, X is selected from the group of
hydrolysable radicals which are other than alkoxy and hydroxyl, a, b and
c are each integers between 0 and 3, and the sum of a, b and c is 3.

10. Block copolymers according to claim 2, characterized in that the
blocks A and/or B may further contain vinyl esters, vinyl ethers,
fumarates, maleates, styrenes, acrylonitriles or other ATRP-polymerizable
monomers.

11. Process for preparing block copolymers of composition ABA with
≦4 silyl groups in the individual A blocks, characterized in that
block A, a copolymer containing silyl-functionalized (meth)acrylates and
monomers selected from the group of (meth)acrylates or mixtures thereof,
and one block B, containing (meth)acrylates or mixtures thereof which
have no additional silyl functionality, are prepared by means of atom
transfer radical polymerization (ATRP) in the presence of an initiator
and of a catalyst in a halogen-free solvent.

12. Process for preparing block copolymers according to claim 11,
characterized in that the initiator is a bifunctional initiator.

13. Process for preparing block copolymers according to claim 12,
characterized in that 1,4-butanediol di(2-bromo-2-methylpropionate),
1,2-ethylene glycol di(2-bromo-2-methylpropionate), diethyl
2,5-dibromoadipate or diethyl 2,3-dibromomaleate is used preferably as
bifunctional initiator.

14. Process for preparing block copolymers according to claim 11 and 13,
characterized in that the block copolymer of composition ABA is prepared
by means of sequential polymerization.

15. Process for preparing block copolymers according to claim 11 to 14,
characterized in that transition metal compounds are used as catalyst.

16. Process for preparing block copolymers according to claim 15,
characterized in that compounds of copper, of iron, of rhodium, of
platinum, of ruthenium or of nickel are used as catalyst.

17. Process for preparing block copolymers according to claim 16,
characterized in that copper compounds are used as catalyst.

18. Process for preparing block copolymers according to claim 15 to 17,
characterized in that prior to the polymerization the catalyst is brought
together with a nitrogen, oxygen, sulphur or phosphorus compound which is
able to form one or more coordinative bonds with the transition metal to
form a metal-ligand complex.

19. Process for preparing block copolymers according to claim 18,
characterized in that N-containing chelate ligands are used as ligand.

20. Process for preparing block copolymers according to claim 19,
characterized in that 2,2'-bipyridine,
N,N,N',N'',N''-pentamethyldiethylenetriamine (PMDETA),
tris(2-aminoethyl)amine (TREN), N,N,N',N'-tetramethylethylenediamine or
1,1,4,7,10,10-hexamethyltriethylenetetramine is used as ligand.

21. Process for preparing block copolymers according to claim 10,
characterized in that the block copolymer has a number-average molecular
weight of between 5000 g/mol and 100 000 g/mol.

22. Process for preparing block copolymers according to claim 10,
characterized in that the block copolymer preferably has a number-average
molecular weight of between 7500 g/mol and 50 000 g/mol.

23. Process for preparing block copolymers according to claim 10,
characterized in that the block copolymer has a molecular weight
distribution of less than 1.6.

24. Process for preparing pentablock copolymers according to claim 10,
characterized in that after the polymerization the catalyst is
precipitated by addition of a sulphur compound and separated from the
polymer solution by filtration.

25. Process for preparing pentablock copolymers according to claim 24,
characterized in that the sulphur compound is a mercaptan or a compound
containing a thiol group.

26. Use of block copolymers of composition ABA with ≦4
silyl-functionalized groups in the individual A blocks, characterized in
that block A, a copolymer containing silyl-functionalized (meth)acrylates
and monomers selected from the group of (meth)acrylates or mixtures
thereof, and one block B, containing (meth)acrylates or mixtures thereof
which have no silyl function, are polymerized as ABA block copolymers, in
reactive hot-melt adhesives or in adhesive bonding compositions.

27. Use of block copolymers of composition ABA with ≦4
silyl-functionalized groups in the individual A blocks, characterized in
that block A, a copolymer containing silyl-functionalized (meth)acrylates
and monomers selected from the group of (meth)acrylates or mixtures
thereof, and one block B, containing (meth)acrylates or mixtures thereof
which have no silyl function, are polymerized as ABA block copolymers, in
sealants for applications in the fields of automotive engineering,
shipbuilding, container construction, mechanical engineering and aircraft
engineering, and also in the electrical industry, in building
applications and in the building of domestic appliances.

28. Use of block copolymers of composition ABA with ≦4
silyl-functionalized groups in the individual A blocks, characterized in
that block A, a copolymer containing silyl-functionalized (meth)acrylates
and monomers selected from the group of (meth)acrylates or mixtures
thereof, and one block B, containing (meth)acrylates or mixtures thereof
which have no silyl function, are polymerized as ABA block copolymers, in
heat-sealing applications.

Description:

[0001] The invention relates to a process for preparing
(meth)acrylate-based ABA triblock copolymers with a silyl
functionalization of the A blocks and to their use for example as binders
in adhesives or sealants.

[0002] Tailor-made copolymers with defined composition, chain length,
molar mass distribution, etc. are a broad field of research. One of the
distinctions made is between gradient polymers and block polymers. A
variety of applications are conceivable for such materials. A number of
them will be briefly presented below.

[0003] Block polymers have a sharp transition between the monomers in the
polymer chain, which is defined as a boundary between the individual
blocks. A typical synthesis process for AB block polymers is the
controlled polymerization of monomer A and, at a later point in time, the
addition of monomer B. Besides sequential polymerization by batchwise
addition to the reaction vessel, a similar result can also be obtained by
sharply altering the compositions of the two monomers, in the case of
their continuous addition, at defined points in time. In this case, a
gradient copolymer is obtained.

[0004] Suitable living or controlled polymerization methods include not
only anionic polymerization or group-transfer polymerization but also
modern methods of controlled radical polymerization such as, for example,
RAFT polymerization. The mechanism of RAFT polymerization is described in
more detail in WO 98/01478 or EP 0 910 587. Application examples are
found in EP 1 205 492.

[0005] A new mode of polymerization brought the art a good deal closer to
the aim of tailor-made polymers. The ATRP method (atom transfer radical
polymerization) was developed in the 1990s definitively by Prof.
Matyjaszewski (Matyjaszewski et al., J. Am. Chem. Soc., 1995, 117, p.
5614; WO 97/18247; Science, 1996, 272, p. 866). ATRP yields narrowly
distributed (homo)polymers in the molar mass range of Mn=10 000-120
000 g/mol. A particular advantage here is that both the molecular weight
and the molecular weight distribution can be regulated. As a living
polymerization, furthermore, it allows the targeted construction of
polymer architectures such as, for example, random copolymers or else
block copolymer structures. By means of corresponding initiators it is
additionally possible to access, for example, unusual block copolymers
and star polymers. Theoretical principles relating to the polymerization
mechanism are elucidated in references including Hans Georg Elias,
Makromolekule, Volume 1, 6th Edition, Weinheim 1999, p. 344.

[0006] Controlled-growth free-radical methods are also suitable
particularly for the targeted functionalization of vinyl polymers.
Particular interest attaches here to silyl functions, among others.
Particularly of interest are functionalizations on the chain ends
(referred to as telechels) or in the vicinity of the chain ends.

[0007] All of these polymers described are prepared either by way of ionic
addition polymerization processes or by polycondensation or polyaddition.
In these processes the preparation of endgroup-functionalized products is
unproblematic. In contrast, the targeted functionalization at the chain
end is virtually impossible in the case of free-radical addition
polymerization. Accordingly, polystyrenes or polymethacrylate have to
date played only a minor part in respect of applications as formulation
constituents for sealants. One possibility for preparing such products
has been added, however, with the development of controlled-growth
free-radical addition polymerization methods such as, for example, that
of ATRP. Accordingly these monomers too are now available for the
construction of corresponding polymer architectures.

[0008] A method already established for preparing silyl-telechelic
polymers--that is, polymers having silyl groups located precisely on the
two chain ends--is the endgroup functionalization of a poly(meth)acrylate
with olefinic groups and the subsequent hydrosilylation of those groups.

[0009] One possibility of providing poly(meth)acrylates synthesized by
ATRP with olefinic functionalization on the endgroups is described in US
2005/0113543. Disadvantages of this process, in which one olefinic group
is introduced by an unsaturated initiator and the other by substitution
of the halogenated chain end by organotin compounds, involving transfer
of an allyl group, are the unavoidable multi-stage character of the
process, the use of toxicologically objectionable tin compounds, and a
monofunctional initiation, which rules out the synthesis of symmetrical
ABA triblock copolymers of the invention.

[0010] The application of a single-stage process for the synthesis of
olefinically terminated poly(meth)acrylates is described in EP 1 085 027.
By adding non-conjugated dienes to a polymerization solution initiated
using a bifunctional ATRP initiator, the polymerization is discontinued
and the product is terminated. The method is described in greater
precision in EP 1 024 153 and EP 1 153 942. Those publications also
describe the use of the materials as an intermediate to a further
reaction to give silyl-terminated products. An analogous reaction, in
which the hydrosilylation and the crosslinking are carried out
simultaneously, is found in EP 1 277 804. All of these descriptions
propose exclusively purely terminated products. None of the polymers
described has a block structure. EP 1 158 006 extends the above-described
termination approaches in a number of respects: on the one hand, the
group of reagents suitable for the termination is expanded to include
cyclic dienes such as cyclooctadienes, for example. This supplementation,
however, is not seen as extending the polymer architecture.

[0011] A great disadvantage of these products as compared with those of
the invention is the two-stage preparation process. Whereas the
copolymerization of silyl-functional monomers in accordance with the
invention provides a simple, one-stage process, the polymer-analogous
reaction described not only is two-stage but additionally necessitates
the implementation, between the actual polymerization and the
hydrosilylation, of a costly and inconvenient product purification
procedure. This purification must be very thorough, since not only
transition metals--from the ATRP process, for example--but also, in
particular, the polyfunctional, usually aminic ligands that are used in
this process have a deactivating effect on the hydrosilylation catalysts
such as the Karstedt catalyst, for example. In comparison with the
single-stage process of the invention, the multistage process that
results from the above is clearly disadvantageous both economically and
environmentally.

[0012] A further disadvantage of these products as compared with polymers
having multiply functionalized, short outer blocks is the greater
probability of obtaining products without functionalization at one end.

[0013] As a result of the lower degree of functionalization that results
in each case in relation to the polymers of the invention, a lower degree
of crosslinking is obtained for further follow-on reactions such as, for
example, in the curing process of sealant formulations, and this lower
degree of crosslinking acts counter to the mechanical stability and
chemical resistance of the seal or adhesive layer.

[0014] An alternative preparation of silyl-terminated products is
described in EP 0 976 766 and in EP 1 059 308. There, in a second process
stage, an endgroup functionalization is carried out. Besides the
above-described disadvantages of telechelic polymers relative to the
block copolymers of the invention, this process is inefficient. To the
skilled person it is readily apparent that the reactions described there
can lead only to a low level of functionalization.

[0015] EP 1 179 567 and EP 1 197 498 describe three-stage processes for
the synthesis of corresponding silyl telechels. By substituting the
terminal halogen atoms with oxyanions, olefinic groups are introduced at
the chain ends. These groups, finally, are hydrosilylated in a third
process step.

[0016] A disadvantage of free-radically prepared binders of this kind
would be a random distribution of the functional groups in the polymer
chain. That leads to a tight crosslinking and hence to reduced elasticity
on the part of the sealant. Furthermore, impairment of substrate bonding
may also result.

[0017] Polymers obtained by a free-radical addition polymerization process
often exhibit molecularity indices of well above 1.6. In the case of a
molecular weight distribution of this kind, therefore, there are
unavoidably very short-chain polymers and extremely long-chain polymers
in the product as a whole. The short-chain by-products can adversely
affect the chemical stability of the product. Long-chain by-products, in
contrast, lead to a disproportionate increase in the viscosity of the
polymer melt or polymer solution. This effect is in no way compensated by
the broad-distribution chains of low molecular mass which are effective
as plasticizers in certain circumstances. These disadvantages of
free-radically polymerized, (meth)acrylate-based binders can be done away
with by the ability, through the use of a controlled polymerization
method, in the form of atom transfer radical polymerization, to make
binders available which have very narrow molecular weight distributions
and which, as compared with free-radically polymerized (meth)acrylates,
have a low fraction of high molecular mass constituents. In polymer
mixtures these constituents in particular bring about an increase in the
viscosity.

[0018] Besides telechels and block structures, ATRP-synthesized
silyl-containing (meth)acrylate copolymers with a random distribution and
a narrow molecular weight distribution represent an alternative. A
disadvantage of such binders over the polymers of the invention is the
close-knit crosslinking, which is entirely advantageous for coating
systems, for example, but which, in the context of formulation in
sealants or adhesives, can lead to an embrittlement of the end product
and hence to a greater sensitivity to ageing.

[0019] Besides ATRP, other methods too are employed for the synthesis of
functionalized polymer architectures. The two relevant methods will be
described briefly below. In this context there is a delimitation from the
present invention in terms of the products and also the methodology.
Particular emphasis is given here to the advantages of ATRP over other
processes:

[0020] DE 38 32 466 describes, among other things, the preparation of
P(AMA)-(MMA)-(AMA) triblock copolymers by means of group transfer
polymerization (GTP). However, in the context of the materials described
in the patent specification it is clearly evident to the skilled person
that these polymers readily tend to premature crosslinking reactions and
thus cannot be storage-stable even with stabilization. Moreover, in order
to obtain silyl-functionalized polymer, it is necessary to carry out a
further step of hydrosilylation. The direct synthesis of
silyl-functionalized polymethacrylates by way of GTP is unknown from the
literature.

OBJECT

[0021] A new stage in the development are the triblock copolymers
described below.

[0022] ABA triblock copolymers are to be equated with 5-block copolymers
of composition ACBCA or CABAC.

[0023] It was an object to prepare triblock polymers of structure ABA. In
particular there is a need for silyl-terminated poly(meth)acrylates
and/or poly(meth)acrylates which in terms of their properties match or
come very close to silyl-terminated materials. This can be achieved, for
example, through the incorporation of one to a few units having silyl
groups at the chain end whose polymerization activity is low or zero.
Chain ends are used as a term for the end segment of a polymer,
accounting for not more than 1-20% by weight of the total weight of the
polymer.

[0024] Poly(meth)acrylates which carry silyl-functional chain ends, or
silyl-terminated poly(meth)acrylates, have suitability as prepolymers for
moisture-curing formulations, e.g. in adhesives or sealant applications.

[0025] A further object of the invention is to provide polymers containing
reactive silyl functionalities, as binders, in such a way that the number
of the silyl groups in the polymer, while retaining effective
availability for the curing reaction, is minimized.

[0026] A further subject of this invention is the functionalization of
short A blocks in ABA triblock copolymers through the incorporation of
suitable unsaturated monomers during the last stage of a sequential
polymerization that have an additional silyl functionality.

[0027] A further object is to provide a material having a very narrow
molecular weight distribution of less than 1.6, preferably less than 1.4.
This minimizes not only the fractions of relatively high molecular mass
constituents, whose effects include contributing to an unwanted increase
in solution or melt viscosity, but also the fractions of particularly low
molecular mass constituents, which can induce deterioration in the
solvent resistance of the binder.

[0028] It is an object of the present invention, therefore, among others,
to provide a binder for sealants that either is silyl-terminated or else
has a small number of free silyl groups in the vicinity of the chain
ends. When formulated in sealants, such materials feature higher
elasticity. This also results in an improvement in adhesion to the
substrate.

[0029] A further object was to provide a binder with which any premature
gelling is prevented.

SOLUTION

[0030] The object has been achieved by the making available of block
copolymers of composition ABA with at least 1 and at most 4 silyl groups
in the individual A blocks, characterized in that block A, a copolymer
containing silyl-functionalized (meth)acrylates and monomers selected
from the group of (meth)acrylates or mixtures thereof, and one block B,
containing (meth)acrylates or mixtures thereof which have no additional
silyl function, are polymerized as ABA block copolymers.

[0031] It has been found that ABA block copolymers having at least 1 and
at most 2 silyl groups in the individual A blocks can also be prepared.

[0032] Both to the copolymers of block A and to the copolymers of block B
it is possible to add 0-50% by weight of ATRP-polymerizable monomers
which are not included in the group of (meth)acrylates.

[0033] One preferred embodiment is represented by block copolymers which,
with an ABA composition, have ≦4 silyl groups in the individual A
blocks and where the block A, a copolymer containing silyl functionalized
(meth)acrylates and monomers selected from the group of (meth)acrylates
or mixtures thereof and, optionally, further, ATRP-polymerizable monomers
which are not included in the group of (meth)acrylates, and one block B,
containing (meth)acrylates or mixtures thereof which have no silyl
function and, optionally, further, ATRP-polymerizable monomers which are
not included in the group of (meth)acrylates, are polymerized as ABA
block copolymers, it also being possible for the ATRP-polymerizable
monomers to be copolymerized only in block A or to be copolymerized only
in block B.

[0034] A further service of the present invention is to provide block
copolymers which have been specifically functionalized at the ends of the
polymer chain.

[0035] As compared with the formulations described in the prior art having
silyl terminated binders in the formulation, the advantage of an improved
crosslink-ability can also be seen in the products of the invention, with
a relevantly higher degree of functionalization. As a result of the
higher number of reactive groups in the chain end segment, reaction of
the silyl groups is more likely, and crosslinking to a comparably
close-knit elastomer or to flexible sealant proceeds at a significantly
faster rate. Targeted control over the crosslinking density and/or the
properties of the crosslinked end product is improved by a distribution
of the functionalities in the end segments. Additionally, distribution of
the reactive groups over the end segments--in this case the blocks
A--rules out excessively close-knit crosslinking. An end segment is a
section of the chain that accounts in each case for not more than 25% by
mass and preferably not more than 10% by mass, and with very particular
preference not more than 5% by mass, of the overall polymer chain.

[0036] The block copolymers are prepared by means of a sequential
polymerization process. In other words, the monomer mixture for the
synthesis of the blocks A, for example, is not added to the system until
the monomer mixture for the synthesis of block B, for example, has
undergone at least 90% reaction, preferably at least 95%. This process
ensures that the B blocks are free from monomers of composition A, and
that the A blocks contain less than 10%, preferably less than 5%, of the
total amount of the monomers of composition B. According to this
definition, the block boundaries are located at the position in the chain
at which the first repeating unit of the metered-in monomer mixture--in
this example, of the mixture A--is located.

[0037] An advantage of the present invention, moreover, is a limited
number of functionalities in the respective functionalized polymer
blocks. A higher fraction of functional groups in the binder leads to
possible premature gelling or at least to an additional increase in the
solution or melt viscosity. This object has been achieved through the
deliberate attachment of the functionalities at the chain end or in the
vicinity thereof.

[0038] A further advantage of the block copolymers is the colorlessness
and the odourlessness of the product produced.

[0039] The possible applications of the materials of the invention
include, however, not only binders for sealants or as intermediate for
the introduction of other kinds of functionalities. EP 1 510 550, for
example, describes a coating composition composed, among other things, of
acrylate particles and polyurethanes. A polymer of the invention in a
corresponding formulation led to an improvement in the processing
properties and to a further alternative of a crosslinking mechanism.
Conceivable applications would include, for example, powder coating
formulations.

[0040] Critical to the success of this process, moreover, is that the
silyl group of the silyl-functional monomer, under polymerization
conditions, enters into a premature crosslinking reaction not at all or
only to a very small extent. The monomers copolymerized for silyl
functionalization are distinguished by the following general formula:

H2C═CR3C(O)O--R4--Si(OR1)bR2aX.su-
b.c

[0041] In this formula the organic radicals R1 and R2 may each
be identical or different to one another. Furthermore, the organic
radicals R1 and R2 are selected from the group of aliphatic
hydrocarbon radicals consisting of 1 to 20 carbon atoms.

[0042] These groups may be alternatively linear, branched or cyclic.
R1 in this case may also exclusively be hydrogen.

[0043] X is selected from the group of hydrolysable radicals which are
other than alkoxy and hydroxyl. This group includes, among others,
halogen, acyloxy, amino, amido, mercapto, alkenyloxy and similar
hydrolysable groups.

[0044] Moreover, a, b and c are each integers between 0 and 3. The sum
a+b+c is 3.

[0045] The radical R3 is hydrogen or an aliphatic hydrocarbon radical
consisting of 1 to 20 carbon atoms. Preferably R3 is hydrogen
(acrylates) or a methyl group (methacrylates).

[0049] A commercially available monomer would be, for example,
Dynasylan® MEMO from Evonik-Degussa GmbH. This compound is
3-methacryloyloxypropyl-trimethoxysilane.

[0050] It is advantageous that the monomers used for the functionalization
are polymerized without there being crosslinking reactions.

[0051] Within the ABA triblock copolymers the B blocks may in turn
inherently have a CDC triblock structure, and, accordingly, the ABA
triblock copolymers would be equated with 5-block copolymers of the
composition ACDCA. In this case the composition of the C blocks
corresponds to the composition of the non-silyl-functionalized fraction
in the A blocks.

[0052] In the ABA triblock copolymers, the individual A blocks may in turn
inherently have a CA' diblock structure. The blocks A' are composed in
turn of silyl-functionalized (meth)acrylates and monomers selected from
the group of (meth)acrylates or mixtures thereof. The composition of the
C blocks differs from the composition of the A' blocks insofar as they
contain no silyl-functionalized monomers. Furthermore, the C blocks are
not restricted in terms of the weight fraction in the polymer as a
whole--in contrast to the A and A' blocks. Accordingly the ABA triblock
copolymers would be equated with 5-block copolymers of the composition
CA'BA'C pentablock copolymers. In this case the composition of the C
blocks corresponds to the composition of the non-silyl-functionalized
fraction in the A' blocks.

[0053] The (meth)acrylate notation stands for the esters of (meth)acrylic
acid and here denotes not only methacrylate, such as methyl methacrylate,
ethyl methacrylate, etc., for example, but also acrylate, such as methyl
acrylate, ethyl acrylate, etc., for example, and also mixtures of both.

[0054] Moreover, a process has been developed for preparing block
copolymers of composition ABA. Using a specific form of living
polymerization, that of atom transfer radical polymerization (ATRP), it
is possible to incorporate well-controlled compositions, architectures
and defined functionalities into a polymer.

[0055] It has been found that through the use of a bifunctional initiator
and a sequential polymerization it is possible to construct ABA, ACDCA or
CA'BA'C structures in a controlled fashion.

[0057] Besides the (meth)acrylates set out above it is possible for the
compositions to be polymerized also to contain further unsaturated
monomers which are copolymerizable with the aforementioned
(meth)acrylates and by means of ATRP. These include, among others,
1-alkenes, such as 1-hexene, 1-heptene, branched alkenes such as, for
example, vinylcyclohexane, 3,3-dimethyl-1-propene,
3-methyl-1-diisobutylene, 4-methyl-1-pentene, acrylonitrile, vinyl esters
such as vinyl acetate, styrene, substituted styrenes with an alkyl
substituent on the vinyl group, such as α-methylstyrene and
α-ethylstyrene, substituted styrenes with one or more alkyl
substituents on the ring such as vinyltoluene and p-methylstyrene,
halogenated styrenes such as, for example, monochlorostyrenes,
dichlorostyrenes, tribromostyrenes and tetrabromo-styrenes; heterocyclic
compounds such as 2-vinylpyridine, 3-vinylpyridine,
2-methyl-5-vinylpyridine, 3-ethyl-4-vinylpyridine,
2,3-dimethyl-5-vinylpyridine, vinylpyrimidine, 9-vinylcarbazole,
3-vinylcarbazole, 4-vinylcarbazole, 2-methyl-1-vinylimidazole,
vinyloxolane, vinylfuran, vinylthiophene, vinylthiolane, vinylthiazoles,
vinyloxazoles and isoprenyl ethers; maleic acid derivatives, such as, for
example, maleic anhydride, maleimide, methylmaleimide and dienes such as
divinylbenzene, for example, and also, in the A blocks, the respective
hydroxy-functionalized and/or amino-functionalized and/or
mercapto-functionalized compounds. Furthermore, these copolymers may also
be prepared such that they have a hydroxyl and/or amino and/or mercapto
functionality in one substituent. Examples of such monomers include
vinylpiperidine, 1-vinylimidazole, N-vinylpyrrolidone,
2-vinylpyrrolidone, N-vinylpyrrolidine, 3-vinylpyrrolidine,
N-vinylcaprolactam, N-vinylbutyrolactam, hydrogenated vinylthiazoles and
hydrogenated vinyloxazoles. Particular preference is given to
copolymerizing vinyl esters, vinyl ethers, fumarates, maleates, styrenes
or acrylonitriles with the A blocks and/or B blocks.

[0059] The block copolymers of composition ABA are prepared by means of
sequential polymerization.

[0060] Besides solution polymerization the ATRP can also be carried out as
emulsion, miniemulsion, microemulsion, suspension or bulk polymerization.

[0061] The polymerization can be carried out under atmospheric,
subatmospheric or superatmospheric pressure. The temperature of
polymerization is also not critical. In general, however, it is situated
in the range from -20° C. to 200° C., preferably from
0° C. to 130° C. and with particular preference from
50° C. to 120° C.

[0062] The polymer of the invention preferably has a number-average
molecular weight of between 5000 g/mol and 100 000 g/mol, with particular
preference between 7500 g/mol and 50 000 g/mol and with very particular
preference ≦30 000 g/mol.

[0063] It has been found that the molecular weight distribution is below
1.6, preferably below 1.4 and ideally below 1.3.

[0064] As bifunctional initiators there can be
RO2C--CHX--(CH2)n--CHX--CO2R,
RO2C--C(CH3)X--(CH2)n--C(CH3)X--CO2R,
RO2C--CX2--(CH2)n--CX2--CO2R,
RC(O)--CHX--(CH2)n--CHX--C(O)R,
RC(O)--C(CH3)X--(CH2)n--C(CH)3X--C(O)R,
RC(O)--CX2--(CH2)n--CX2--C(O)R,
XCH2--CO2--(CH2)n--OC(O)CH2X,
CH3CHX--CO2--(CH2)n--OC(O)CHXCH3,
(CH3)2CX--CO2--(CH2)n--OC(O)CX(CH3)2,
X2CH--CO2--(CH2)n--OC(O)CHX2,
CH3CX2--CO2--(CH2)n--OC(O)CX2CH3,
XCH2C(O)C(O)CH2X, CH3CHXC(O)C(O)CHXCH3,
XC(CH3)2C(O)C(O)CX(CH3)2, X2CHC(O)C(O)CHX2,
CH3CX2C(O)C(O)CX2CH3, XCH2--C(O)--CH2X,
CH3--CHX--C(O)--CHX--CH3,
CX(CH3)2--C(O)--CX(CH3)2, X2CH--C(O)--CHX2,
C6H5--CHX--(CH2)n--CHX--C6H5,
C6H5--CX2--(CH2)n--CX2--C6H5--CX.-
sub.2--(CH2)n--CX2--C6H5, o-, m- or
p-XCH2-Ph-CH2X, o-, m- or p-CH3CHX-Ph-CHXCH3, o-, m-
or p-(CH3)2CX-Ph-CX(CH3)2, o-, m- or
p-CH3CX2-Ph-CX2CH3, o-, m- or
p-X2CH-Ph-CHX2, o-, m- or
p-XCH2--CO2-Ph-OC(O)CH2X, o-, m- or
p-CH3CHX--CO2-Ph-OC(O)CHXCH3, o-, m- or
p-(CH3)2CX--CO2-Ph-OC(O)CX(CH3)2,
CH3CX2--CO2-Ph-OC(O)CX2CH3, o-, m- or
p-X2CH--CO2-Ph-OC(O)CHX2 or o-, m- or
p-XSO2-Ph-SO2X (X stands for chlorine, bromine or iodine; Ph
stands for phenylene (C6H4); R represents an aliphatic radical
of 1 to 20 carbon atoms, which may be linear, branched or else cyclic in
structure, may be saturated or mono- or polyunsaturated and may contain
one or more aromatics or else is aromatic-free, and n is a number between
0 and 20). Preference is given to using 1,4-butanediol
di(2-bromo-2-methylpropionate), 1,2-ethylene glycol
di(2-bromo-2-methylpropionate), diethyl 2,5-dibromoadipate or diethyl
2,3-dibromomaleate. The ratio of initiator to monomer gives the later
molecular weight, provided that all of the monomer is reacted.

[0065] Catalysts for ATRP are set out in Chem. Rev. 2001, 101, 2921. The
description is predominantly of copper complexes--among others, however,
compounds of iron, of rhodium, of platinum, of ruthenium or of nickel are
employed. In general it is possible to use any transition metal compounds
which with the initiator, or with the polymer chain which has a
transferable atomic group, are able to form a redox cycle. Copper can be
supplied to the system for this purpose, for example, starting from
Cu2O, CuBr, CuCl, CuI, CuN3, CuSCN, CuCN, CuNO2,
CuNO3, CuBF4, Cu(CH3COO) or Cu(CF3COO).

[0066] One alternative to the ATRP described is represented by a variant
of it: in so-called reverse ATRP, compounds in higher oxidation states
can be used, such as CuBr2, CuCl2, CuO, CrCl3,
Fe2O3 or FeBr3, for example. In these cases the reaction
can be initiated by means of conventional free-radical initiators such
as, for example, AIBN. In this case the transition metal compounds are
first reduced, since they are reacted with the radicals generated from
the conventional free-radical initiators. Reverse ATRP has been described
by, among others, Wang and Matyjaszewski in Macromolecules (1995), vol.
28, p. 7572 ff.

[0067] One variant of reverse ATRP is represented by the additional use of
metals in the zero oxidation state. As a result of an assumed
comproportionation with the transition metal compounds in the higher
oxidation state, an acceleration is brought about in the reaction rate.
This process is described in more detail in WO 98/40415.

[0068] The molar ratio of transition metal to bifunctional initiator is
generally situated in the range from 0.02:1 to 20:1, preferably in the
range from 0.02:1 to 6:1 and with particular preference in the range from
0.2:1 to 4:1, without any intention hereby to impose any restriction.

[0069] In order to increase the solubility of the metals in organic
solvents and at the same time to prevent the formation of stable and
hence polymerization-inert organometallic compounds, ligands are added to
the system. Additionally the ligands facilitate the abstraction of the
transferable atomic group by the transition metal compound. A listing of
known ligands is found for example in WO 97/18247, WO 97/47661 or WO
98/40415. As a coordinative constituent, the compounds used as ligand
usually contain one or more nitrogen, oxygen, phosphorus and/or sulphur
atoms. Particular preference is given in this context to nitrogen
compounds. Very particular preference is enjoyed by nitrogen-containing
chelate ligands. Examples that may be given include 2,2'-bipyridine,
N,N,N',N'',N''-pentamethyldiethylenetriamine (PMDETA),
tris(2-aminoethyl)amine (TREN), N,N,N',N'-tetramethylethylenediamine or
1,1,4,7,10,10-hexamethyltriethylenetetramine. Valuable indicators
relating to the selection and combination of the individual components
are found by the skilled person in WO 98/40415.

[0070] These ligands may form coordination compounds in situ with the
metal compounds or they may first be prepared as coordination compounds
and then introduced into the reaction mixture.

[0071] The ratio of ligand (L) to transition metal is dependent on the
density of the ligand and on the coordination number of the transition
metal (M). In general the molar ratio is situated in the range 100:1 to
0.1:1, preferably 6.1 to 0.1:1 and with particular preference 3:1 to 1:1,
without any intention hereby to impose any restriction.

[0072] When ATRP has taken place, the transition metal compound can be
precipitated by the addition of a suitable sulphur compound. By addition
of mercaptans, for example, the halogen atom at the end of the chain is
substituted, with release of a hydrogen halide. The hydrogen halide--HBr,
for example--protonates the ligand L, coordinated on the transition
metal, to form an ammonium halide. As a result of this process, the
transition metal-ligand complex is quenched and the "bare" metal is
precipitated. After that the polymer solution can easily be purified by
means of a simple filtration. The said sulphur compounds are preferably
compounds containing an SH group. With very particular preference they
are one of the regulators known from free-radical polymerization, such as
ethylhexyl mercaptan or n-dodecyl mercaptan. To increase the degree of
silyl functionalization it is also possible to use silyl mercaptans such
as, for example, 3-mercaptopropyltrimethoxysilane, which can be obtained
as Dynasylan® MTMO from Evonik AG.

[0073] A broad field of application is produced for these products. The
selection of the use examples is not such as to restrict the use of the
polymers of the invention. The examples are intended merely to serve as
random samples of the broad functional capacity of the polymers
described. Block copolymers of the composition ABA, ACBCA, CABAC or CDBDC
are employed preferably as prepolymers for a moisture-curing
crosslinking. The prepolymers can be crosslinked with any desired
polymers. D blocks are polymer blocks which on the one hand correspond in
their basic composition to the B block, and not to the C blocks, and on
the other hand contain silyl-functional units.

[0074] The preferred applications for the block copolymers of the
invention with ABA, ACBCA, CDBDC or CA'BA'C with ≦4 silyl groups
in the individual A or D blocks are to be found in sealants, in reactive
hot-melt adhesives or in adhesive bonding compositions. Particularly
appropriate uses are in sealants for applications in the fields of
automotive engineering, shipbuilding, container construction, mechanical
engineering and aircraft engineering, and also in the electrical industry
and in the building of domestic appliances. Further preferred fields of
application are those of sealants for building applications, heat-sealing
applications or assembly adhesives.

[0075] With the new binders it is possible to prepare one-component and
two-component elastomers for example for one of the recited applications.
Typical ingredients of a formulation are the binder, solvents, fillers,
pigments, plasticizers, stabilizing additives, water scavengers, adhesion
promoters, thixotropic agents, crosslinking catalysts, tackifiers, etc.

[0076] In order to reduce the viscosity it is possible to use solvents,
examples being aromatic hydrocarbons (e.g. toluene, xylene, etc.), esters
(e.g. ethyl acetate, butyl acetate, amyl acetate, Cellosolve acetate,
etc.), ketones (e.g. methyl ethyl ketone, methyl isobutyl ketone,
diisobutyl ketone, etc.), etc. The solvent may be added as early as
during the free-radical polymerization.

[0078] The examples given below are given for the purpose of improved
illustration of the present invention, but are not apt to restrict the
invention to the features disclosed herein.

EXAMPLES

[0079] The number-average and weight-average molecular weights, Mn and Mw,
and the molecular weight distributions, Mw/Mn, are determined by means of
gel permeation chromatography (GPC) in tetrahydrofuran against a PMMA
standard.

Example 1

[0080] A jacketed vessel equipped with stirrer, thermometer, reflux
condenser, nitrogen introduction tube and dropping funnel was charged
under an N2 atmosphere with monomer 1 a (precise identification and
quantity in Table 1), 125 ml of propyl acetate, 0.5 g of copper(I) oxide
and 1.3 g of N,N,N',N'',N''-pentamethyl-diethylenetriamine (PMDETA). The
solution is stirred at 80° C. for 15 minutes. Subsequently, at the
same temperature, 1,4-butanediol di(2-bromo-2-methylpropionate) (BDBIB;
for amount see Table 1) initiator in solution in 25 ml of propyl acetate
is added dropwise. After the polymerization time of three hours a sample
is taken for determination of the average molar weight Mn (by means
of SEC) and a mixture of monomer 2a and monomer 3a (precise
identification and quantity in Table 1) is added. The mixture is
polymerized to an anticipated conversion of at least 95% and is
terminated by addition of 2.1 g of n-dodecyl mercaptan. The solution is
worked up by filtration over silica gel and the subsequent removal of
volatile constituents by means of distillation. The average molecular
weight is determined, finally, by SEC measurements. The fraction of
incorporated monomer 3a is quantified by means of 1H NMR
measurements.

Example 2

[0081] In the same way as in Example 1, monomers 1b, 2b and 3b (precise
identification and quantity in Table 1) are used.

Example 3

[0082] In the same way as in Example 1, monomers 1c, 2c and 3c (precise
identification and quantity in Table 1) are used.

Example 4

[0083] In the same way as in Example 1, monomers 1d, 2d and 3d (precise
identification and quantity in Table 1) are used.

[0084] Whereas the molecular weight distributions of the first stage are
monomodal, the distributions of the final stages exhibit a more or less
pronounced high molecular mass shoulder. The latter are attributable to
side reactions of the silyl groups with partial chain dimerization. After
removal of the solvent, the products can be stabilized by adding suitable
desiccants. In this way it is possible to ensure good storage stability
without a further increase in molecular weight.

Example 5

[0085] A jacketed vessel equipped with stirrer, thermometer, reflux
condenser, nitrogen introduction tube and dropping funnel was charged
under an N2 atmosphere with monomer la (precise identification and
quantity in Table 2), 145 ml of propyl acetate, 0.62 g of copper(I) oxide
and 1.6 g of N,N,N',N'',N''-penta-methyldiethylenetriamine (PMDETA). The
solution is stirred at 80° C. for 15 minutes. Subsequently, at the
same temperature, 1,4-butanediol di(2-bromo-2-methylpropionate) (BDBIB;
for amount see Table 1) initiator in solution in 30 ml of propyl acetate
is added dropwise. After the polymerization time of three hours a sample
is taken for determination of the average molar weight Mn (by means
of SEC) and monomer IIa (precise identification and quantity in Table 2)
is added. After a calculated 95% conversion, finally, a mixture of
monomer IIa' and monomer IIIa (for precise identification and amount see
Table 2) is added. The mixture is polymerized to an anticipated
conversion of at least 95% and is terminated by addition of 2.4 g of
n-dodecyl mercaptan. The solution is worked up by filtration over silica
gel and the subsequent removal of volatile constituents by means of
distillation. The average molecular weight is determined, finally, by SEC
measurements. The fraction of incorporated monomer 3a is quantified by
means of 1H NMR measurements.

Example 6

[0086] A jacketed vessel equipped with stirrer, thermometer, reflux
condenser, nitrogen introduction tube and dropping funnel was charged
under an N2 atmosphere with monomer Ib (precise identification and
quantity in Table 2), 150 ml of propyl acetate, 0.60 g of copper(I) oxide
and 1.6 g of N,N,N',N'',N''-penta-methyldiethylenetriamine (PMDETA). The
solution is stirred at 80° C. for 15 minutes. Subsequently, at the
same temperature, 1,4-butanediol di(2-bromo-2-methylpropionate) (BDBIB;
for amount see Table 1) initiator in solution in 35 ml of propyl acetate
is added dropwise. After the polymerization time of three hours a sample
is taken for determination of the average molar weight Mn (by means
of SEC) and a mixture of monomer IIb and monomer IIIb (precise
identification and quantity in Table 2) is added. After a calculated 95%
conversion, finally, monomer IIb' (for precise identification and amount
see Table 2) is added. The mixture is polymerized to an anticipated
conversion of at least 95% and is terminated by addition of 2.4 g of
n-dodecyl mercaptan. The solution is worked up by filtration over silica
gel and the subsequent removal of volatile constituents by means of
distillation. The average molecular weight is determined, finally, by SEC
measurements. The fraction of incorporated monomer 3a is quantified by
means of 1H NMR measurements.

[0087] In the case of the pentablock copolymers as well, the molecular
weight distribution increases after the polymerization stages containing
Dynasylan® MEMO, and in the eluogram there is a more or less strongly
pronounced high molecular mass shoulder discernible.